New Delhi, May 30: The government has refused to investigate thousands of suspected deaths from chikungunya while repeatedly asserting in Parliament that no one has died from this viral infection, public health experts say.

The disease had broken out in many places in 2006, and at least one city recorded an extraordinarily high mortality. Ahmedabad registered 2,944 deaths over its average during a four-month period when the outbreak had peaked, municipal records show.

Such unusually high mortality rates are normally associated with epidemics or natural calamities, said Dileep Mavalankar, professor of public health at the Indian Institute of Management, Ahmedabad. But these excess deaths have never been properly investigated.

Mavalankar said he had sent several written requests to the health ministry for a detailed investigation to find the cause of the deaths, which even today remain unanswered.

During the 2006 outbreak, more than 1.4 million people were suspected to have been infected by chikungunya, a viral disease spread by mosquitoes.

Several patients had developed brain complications and died, a government medical researcher said. But health officials claim these deaths occurred only because the infected people were aged.

Health minister Anbumani Ramadoss has told Parliament at least 10 times over the past 18 months that no death in India can be attributed to chikungunya.

The governments top official responsible for tracking mosquito-borne diseases said chikungunya officially remains a non-fatal disease.

We stand by what we have informed Parliament, said G.P.S. Dhillon, director of the National Vector-Borne Disease Control Programme.

But Mavalankar is surprised that the deaths were not investigated only because the patients were aged.

Imagine not investigating a hit-and-run case only because the victim is an old person who may have had difficulty in crossing the road, he said.

Mavalankar and his colleagues at IIM Ahmedabad spent months analysing municipal death records and have recently highlighted the unusual mortality rise in Ahmedabad from August to November 2006 in the journal Emerging Infectious Diseases.

Chikungunya had re-emerged in India in 2006 after 32 years. Public health experts believe the virus spread to India from Reunion Island in the Indian Ocean, where it had raged for several months and killed 254 people.

Last year too, there were nearly 56,000 cases, mainly in Kerala and Bengal.

Sanchita Bakshi, director of health services in Bengal, said 20,000 people were infected with chikungunya in the state in 2007-08 but none had died of the disease.

Many hospital authorities were afraid to stamp a death case as chikungunya without a positive blood test, Mavalankar said. He described the central governments attitude as shocking.

While the Centre has steadfastly maintained that no one ever died of chikungunya, the Gujarat government had in 2006 told the Assembly that 11 people had died of the disease.

When this inconsistency was pointed out to Dhillon, he said: Why dont you ask the Gujarat government?